Field of Invention
The present invention relates to a memory structure. More particularly, the present invention relates to a non-volatile memory structure and related circuits.
Description of Related Art
Memory is an important component in a computer, and many different memory structures have been developed for different applications. For example, the memory structures include dynamic random access memory (DRAM), static random-access memory (SRAM), read-only memory (ROM), flash memory, etc.
Among the memory structures, the ROM and the flash memory belong to non-volatile memory which can retain data when powered off. In general, these two types of non-volatile memory are relatively stable and have less power consumption when storing data, but they are not easy to overwrite and have slower read/write speeds.
Volatile memories such as DRAM and SRAM are generally taken as the main memory incorporated with a central processing unit (CPU) because they have faster read/write speeds. The advantages of DRAM are simple structure (only a transistor and a capacitor are required), high storage density, and lower cost per unit of capacity. In practical, the capacitor of DRAM is periodically charged, and thus it has a disadvantage of higher power consumption.
Compared with DRAM, SRAM retains the stored data without periodically charging the capacitor when powered on. In addition, SRAM generally has faster read speed (higher than DRAM) and very low power consumption. When powered off, the data stored in a conventional SRAM is lost. The conventional SRAM composed of six transistors still has some issues. For example, when a static noise margin (SNM) of the memory cell is not enough, a storage node is vulnerable to the noise from an external bit line, and thus the original stored data is damaged when it is read. Therefore, there is still much to improve for the conventional SRAM.
Along with the trend of thin and light for mobile devices, the space for the electrical device is extremely limited, and the issue of the power consumption gets people's attentions even more. A suitable memory which is capable of providing higher data stability and faster reading speed, and is additionally capable of solving the problems existing in the conventional SRAM is required.